Once considered a novelty or luxury, portable electronic devices have become prevalent throughout society. Billions of people own portable electronic devices including cellphones, smartphones, tablet computers, laptops, personal digital assistants, personal health meters, personal music players, or wearable cameras. As technology advances, the number and types of portable electronic devices is expected to increase significantly. For instance, smart eyewear and smartwatches are on the verge of becoming mainstream. One common thread among these devices is that they all operate on a battery that provides sufficient power ranging from a few hours to a few days.
Kinetic energy harvesting devices have been developed to provide a remote or portable source of energy for the billions of portable electronic devices. The goal of these energy harvesting devices is to extend the battery life of the portable devices when a user does not have ready access to an electrical outlet. Advertisements show kinetic energy harvesting devices being used on camping trips, travel to exotic locations, emergency situations, business meetings, and in a car/airplane. However, known kinetic energy harvesting devices have not become widely adopted because these devices are generally inefficient, ineffective, and/or cumbersome.
Generally, known kinetic energy harvesting devices use rotatory generators, thermoelectric technologies, or photovoltaic technologies to charge a battery or a portable device directly. However, each device requires a specific kinetic activity to adequately capture energy. For instance, some rotatory-based devices require a user to shake or make a swirling motion with their hand. Other energy harvesting devices are required to be strapped onto a user's shoe or worn on their wrist, which is oftentimes uncomfortable. These devices may adequately capture energy while a user is making the intended motion. However, users oftentimes become weary of making the same motion long enough for the device to capture enough energy. Really, how long is a user expected to rapidly shake their hand in public to supposedly charge a device!
Other energy harvesting devices such as thermoelectric and photovoltaic devices are configured to passively capture energy from heat, light, etc. While these devices are adequate for charging a wristwatch (not a smartwatch), these devices are not adequate or efficient enough to capture sufficient energy to charge a portable electronic device. Some manufacturers have attempted to improve energy harvesting by increasing the size of the energy harvesting actuator/transducer. However, the increased size reduces the portability and comfort of using/wearing these energy harvesting devices.